Seals, such as polytetrafluoroethylene (PTFE) seals, that are of a one-piece design having a continuous, unbroken, or cut section (similar to an o-ring) are commonly used for various sealing applications. Generally, the seals must be stretched over a mandrel or other similar device to properly position the seal into a groove on the outside diameter of the part to be sealed. Because of the physical properties of some materials, the seal stretches over time to a diameter greater than its original diameter. After stretching, the seal generally does not return to its original size. As a result, the seal is ineffective and is frequently discarded.
Prior art attempts to compress the seals to their original diameter have failed or at least have suffered from several deficiencies. For example, one common apparatus for returning seals to their original diameter utilizes a metal collet. As shown in FIGS. 1 and 2, a metal collet 5 is typically used to size seals. The metal collet 5 has segmented jaws spaced radially about the surface of the metal collet 5. Generally, force is applied to push the seal radially from the outside diameter inward to retract the seal to its original diameter. Essentially, the seal is “squeezed” to its original size and shape. However, these metal collets 5 are problematic for a number of reasons.
First, as shown in FIGS. 1-2, the metal collet 5 is typically made from a single continuous piece of spring-tempered steel. The metal collet 5 has relief cuts 6 (or kerfs) that permit steel sections 7 to move radially inward and outward with respect to the interior of the metal collet 5. Typically, the metal collet 5 is only designed to move a few thousandths of an inch. However, seals frequently expand more than a few thousandths of an inch from their original diameter. In such instances, the metal collet 5 is unable to return the seal to its original diameter. If the metal collet 5 is constructed so that it can expand further than a few thousandth of an inch, the metal collet 5 frequently fails due to material fatigue, which is not conducive to high volume manufacturing.
In addition, as the steel sections 7 move together, the kerfs 6 radially contract and are reduced from a gap of considerable size to a very narrow gap in order to squeeze the seals. However, the contraction of the kerfs 6 tends to pinch the seals resulting in damage and weakening of the seals. For example, the kerfs 6 compress the seal material between the gaps and frequently create witness lines and indentations along the seal that causes the seals to fail.
The metal collet 5 is a fixed geometry tool. In other words, the metal collet 5 has a fixed shape and is sized for one specific diameter. A fixed geometry tool, such as the metal collet 5, cannot accommodate the different compressability factors involved in sizing two or more differently sized seals. As a result, the metal collet 5 is not practical for sizing seals of varying diameters at the same time. The metal collet 5 is, instead, only designed to compress one type of seal and to compress the seal an amount equal to the range of movement of the metal collet 5.
Therefore, there is a need in the art for an improved apparatus and method for sizing seals. For example, there is a need in the art for an improved apparatus capable of sizing different sized seals with a single apparatus. In addition, there is a need in the art for an apparatus capable of sizing seals without risk of damage or weakening of the seals. There is also a need in the art for an apparatus for sizing seals that is capable of simultaneously sizing more than one type and sized seal.
Additional information will be set forth in the description which follows, and in part will be obvious from the description or may be learned by practice of the invention.